Hypersonic flight is often characterized as flight through the atmosphere at speeds above Mach 5. At these speeds, aerodynamic heating of the leading surfaces of the aircraft become problematic. Aerodynamic heating is the heating of a body produced by the flow of a fluid (e.g., air) over the body.
In hypersonic flight, the speed of the air molecules impinging on the aircraft rapidly falls to zero near the leading edges of the aircraft. Heating of the leading surfaces occurs as the kinetic energy of the air molecules is converted into thermal energy. The thermal energy heats the leading surfaces, which can transfer heat to other portions of the aircraft (e.g., electronics onboard the aircraft). At hypersonic speeds, the temperature of the leading surfaces can exceed 1000 degrees Celsius. Considerable effort has been made in the last few decades attempting to solve problems associated with aerodynamic heating of hypersonic vehicles.